Aircraft are utilized to deliver equipment and personal to a variety of locations. Helicopters often land at onshore and offshore helipads which are designated landing areas for helicopters providing a clearly marked hard surface. The direct surroundings of a helipad are not always clear of obstacles and that is one of the reasons why visual reference is required for any operations close to the helipad. The Federal Aviation Administration (FAA) regulations allow part of the approach operation to be performed in low visibility conditions, but at some distance from the helipad visual reference must be obtained.
In one aircraft application, helicopters flying instrument flight rules (IFR) during offshore operations (e.g., approaching an offshore platform such as an oil drilling rig, an oil pumping platform, or a ship) must avoid fixed and moving obstacles and see the intended offshore platform for landing. IFR offshore operations often occur in low visibility conditions, such as, heavy fog associated with maritime environments (e.g., maritime fog). Offshore operations can occur in environments with moving ships having heights up to 400 feet. The missed operation point (MOP) for offshore operations is generally 0.6-0.7 nautical miles (NM) from an offshore helipad or platform.
According to a Delta 30° Offshore Standard Instrument Operation (OSIO), a helicopter or rotary wing aircraft approaching an offshore platform is flown into the wind and at a distance of 1.1 NM from the landing site, a delta 30° turn is made either to the right or left depending on the clear area determined by the helicopter operator based on the image provided by the onboard weather radar. When visual reference with the landing site is established before reaching the MOP at 0.6 NM, the pilot proceeds visually to the landing area, otherwise a missed operation must be executed at the MOP.
According to a Parallel Offset OSIO, a helicopter approaching an offshore helipad or platform is flown into the wind and at a distance of 5 NM from the landing site, either a left or right turn is made based on the clear area determined by the helicopter operator based on the image provided by the onboard weather radar. An offset path of 0.5 NM to the left or right of the landing site is established before reaching the decision point altitude at no less than 2 NM from the landing site. The helicopter is flown along the offset path to a 0.7 NM MOP. When visual reference with the landing site is established before reaching the MOP at 0.7 NM from the landing site, the pilot proceeds visually to the landing area, otherwise a missed operation must be executed at MOP. Offshore helicopter approach operations are discussed in the FAA's Advisory Circular AC 90-80B “Approval of Offshore Helicopter Approaches” (Apr. 19, 1992) and “Airborne Radar Approach FAA/NASA Gulf of Mexico Helicopter Flight Test Program,” Department of Transportation, (Report No. AFO-507-78-2, January 1980). The new nomenclature of the draft Advisory Circular AC 90-80C “Approval of Offshore Standard Instrument Operations, Airborne Radar Operations, and Helicopter En Route Descent Areas” has been adopted, instead of using the nomenclature of the current AC 90-80B.